only one answer 7. A certain mutagen causes a specific base change, resulting in

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only one answer

7. A certain mutagen causes a specific base change, resulting in non-complementary base pairing and a point mutation. The mutagen does not affect every instance where this base occurs, but it causes the same base change in each case. In each case below, the mutation occurred on the nontemplate strand of DNA. What base change is caused by this mutagen? The coding dictionary is provided on the last page of this homework. a. G changed to A b. G changed to T c. T changed to C d. A changed to G Case 1. Wild Type trp-thr-pro-arg ala Mutant: trp-thr-pro-his-ala Case 2. Wild Type: leu-as Mutant leu-asn-arg ala-ser Case 3. Wild Type ser-thr-gly-trp-thr Mutant: ser-thr-gly

Explanation / Answer

Here , the answer is (a), mutagen change G base to A.

In case 1 coding sequence is wild type TGG ACG CCA AGA GCG

mutant TGG ACG CCA CAT GCG

In case 2 coding sequence is wild type CTA GAT AGA GCG TCC

mutant CTA AAT AGA GCG TCC

In case 3 coding sequence is wild type TCC ACG GGT TGG ACG

mutant TCC ACG GGT TGA

In all these cases one base change is comman that is G to A. In first case arginine replace by histidine. So, the coading sequence of arginine use either AGA or AGG and histidine CAT or CAC , in both code G changed to A.

In case 2 aspartate converted to asparagine, here bases either GAT or GAC for aspartate and AAT or AAC for asparagine, In both codes G changed to A.

In case 3 Here, muation cause the presence of stop codon so translation stops in mutant. Presence of TGA means during transcription and translation it is UGA which act as a stop codon.

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